The sankey trailers can be purchased from ebay for about £200. They require converting to 12v but this is just a case of changing the bulbs. For it to look a bit better its worth colour coding to vehicle. My one is black and i just used gloss paint. Also worth putting check plate around the edge at a cost of about £30 - 50. I think you can build one for under £500 including the cost of the trailer as long as you can do the work your self. I have just added to my one over the last 6 months so i havn't really noticed a big financial outlay. See the pics in the defender pic gallery of my trailer. I have more pics if you require?
How exactly does the scaffold plank thing work? Mine's a 7 seater CSW 90 - how do you get round the front seats rising above the bulkhead? What do you rest the planks on? I can see this working in a 110, but in a 90?
mine rest on the long wheel arch sections (side to side), creating a flat area on top with a storage area underneath - the fact that the front seats are higher than the bulkhead doesnt matter as the planks dont sit anywhere near that height.